Project Summary Integration of sensory information with motor commands allows movement to be adaptable. For example, many survival-critical orofacial behaviors (chewing, drinking, breathing, etc.) involve updating movement trajectories based on interaction with objects (e.g. matching chewing patterns to food material properties). Proprioceptors, which are sensory afferents that provide information about body position, likely play critical roles in this process. However, given that most past recording of proprioceptors was not performed in awake animals, a clear understanding of proprioceptor movement coding in the awake context is lacking. This project will target and record from mouse jaw-innervating proprioceptors (which lie in the hindbrain mesencephalic trigeminal (MeV) nucleus) during orofacial behavior and test their functional role. Aim 1 will characterize the functional organization of mouse MeV afferents while developing genetic tools for targeting this population. Aim 2 will record from MeV neurons in behaving animals during high-resolution movement tracking. Using this dataset, a systematic quantitative model will be built for MeV neuron activity during voluntary orofacial behavior. Aim 3 will perturb MeV neuron activity to understand the functional role of MeV neurons in orofacial behavior. Completion of this project will involve high-level training in in vivo physiology, behavioral analysis, and systems/computational techniques. This training will draw upon a rich environment for neural circuit and systems research, especially based on the expertise in sensory and motor systems neuroscience in the labs of the Sponsor and Co-Sponsor. Collectively, the proposed project will define the information coding properties of proprioceptors during orofacial movement as well as probe the functional role of this information during behavior. These results could inform strategies for treatment of jaw motor problems seen in the clinic (i.e. denture-wearing patients, temporomandibular joint disorders, etc.). More broadly, this work can provide novel insights into the role of proprioceptive information in motor control, which has wide-ranging implications for the fundamental understanding of movement in healthy and pathological contexts.